Conventional reciprocating engines employ a crank shaft which has been known since the days of the Watt steam engine. One or more pistons which reciprocate in cylinders, are connected to a common crank shaft by means of connecting rods. The lower end bearings (big ends) of the connecting rods are rotatably connected to crank pin portions of the crank shaft. The crank pins and big ends rotate about a path, concentric with the crank shaft itself.
It is well known that the system described is inefficient in many respects. Power is usually developed on the piston, when it is at the top of its stroke. In this position, the connecting rod is aligned directly with the crank pin on the crank shaft.
The piston does not develop rotational power until the crank pin passes its top dead centre position. The maximum force is clearly developed while the crank pin is rotating through its downward stroke (power stroke), and progressively diminishes when it reaches bottom dead centre. Variations in power may also arise due to expansion of the combustion gases during downward movement of the piston.
All of this is too well known to bear repetition.
Numerous proposals and attempts have been put forward to improve the efficiency of the conventional reciprocating engine. Most of them have failed due to either excessive complexity, or excessive wear, or both.
Various examples are shown in US patents.